jruby with 1.9 mode as the default with rvm

Thanks to recent commits from Wayne, you can now pass a build flag when install jruby with rvm and it will build jruby instead of downloading a prebuilt copy. Make sure you rvm get head && rvm reload first. Then we can install jruby with 1.9 mode as the default:

rvm install jruby -C -Djruby.default.ruby.version=1.9

And if you want to use jruby-head:

rvm install jruby-head -C -Djruby.default.ruby.version=1.9

Speeding up jruby with nailgun

I had always wondered why when I installed jruby using rvm it always built something called Nailgun but I never bothered to search about it.

That was a mistake.

Nailgun is an amazing idea that greatly speeds up the start up time of the JVM and subsequently: jruby.

Without Nailgun

$ time jruby -e ''

real        0m1.336s
user        0m2.608s
sys         0m0.205s

With Nailgun

$ time jruby --ng -e ''

real        0m0.265s
user        0m0.001s
sys         0m0.003s

As you can see, nailgun reduced the start up time for jruby by 500%. Now you may be asking “How do I get started using nailgun?”. Well, if you are using rvm then all you need to do is enable the after_use_jruby hook which will start up a nailgun server for you.

chmod +x "$rvm_hooks_path/after_use" "$rvm_hooks_path/after_use_jruby"

And that’s all you need to do. rvm jruby or rvm use jruby will now start up a nailgun server if there isn’t one running and it set the --ng switch for all jruby runs.

If you aren’t using rvm, you will have to compile nailgun and start up a nailgun server with jruby --ng-server. Now whenever you run jruby you just add the --ng switch and it will use the nailgun server. You may want to export JRUBY_OPTS="--ng" to set the switch for all jruby runs.